Pen



FIG. 1 is a top plan view of a pen showing my new design;

FIG. 2 is a bottom plan view;

FIG. 3 is a right side elevational view;

FIG. 4 is a left side elevational view;

FIG. 5 is a front elevational view;

FIG. 6 is a rear elevational view; and,

FIG. 7 is a front perspective view. 

I claim, the ornamental design for a pen, as shown and described. 